The present invention relates generally to an internal combustion engine, and more particularly to an engine having a main and an auxiliary combustion chamber, as well as an intake valve to control the supply of air-fuel mixture into the main and auxiliary combustion chambers.
For the purpose of reducing the amount of harmful exhaust gas from internal combustion engines, particularly from car engines, there have been proposed diverse types of improvements of the internal combustion engines. One resulting internal combustion engine is of the type in which a main and an auxiliary combustion chamber are disposed in each cylinder so that a stratified combustion of an air-fuel mixture takes place in each cylinder of the internal combustion engine. With the internal combustion engine having main and auxiliary combustion chambers, there have been proposed different types of arrangements for carrying out the supply of the air-fuel mixture into the main and auxiliary combustion chambers. Among these different arrangements, one has been proposed by the present inventors, in which arrangement the air-fuel mixture is introduced into the main and auxiliary combustion chambers through a common intake port and, therefore, a single intake valve provided in the common intake port operates to control the duration of the supply of the air-fuel mixture to both chambers. This type of air-fuel mixture supply arrangement has brought about a practical advantage that the structure and the assembly of an internal combustion engine can be very simple.
The internal combustion engine including the air-fuel mixture supply arrangement of the type described above is characterized in that the auxiliary combustion chamber is formed with a suction aperture through which the auxiliary combustion chamber receives the air-fuel mixture supplied via the intake port during the intake stroke, and a discharge aperture through which residual gas in the auxiliary combustion chamber is discharged or exhausted. Thus, positive exhaustion of the residual gas from the auxiliary combustion chamber as well as filling of a fresh air-fuel mixture into the entire space of the auxiliary combustion chamber are always attained.
The internal combustion engine of the type described above is also characterized in that the engine may have such a modified arrangement that the afore-mentioned auxiliary combustion chamber is furnished with an air-fuel mixture richer than that for the main combustion chamber as necessary. The modified arrangement may be realized by providing the internal combustion engine with a separate passageway for enabling the introduction of the richer air-fuel mixture into the auxiliary combustion chamber. In this case, the separate passageway will be arranged so as to also open into the intake port provided for lean air-fuel mixture or air to be introduced into the main combustion chamber. The modified arrangement may also be realized by providing the internal combustion engine with a fuel injection nozzle installed in the intake port.
The internal combustion engines of the type described above are disclosed in, for example, the publicly disclosed Japanese Pat. Nos. 96108/1974, 111008/1975, and 124405/1974. However, it should be noted that in the internal combustion engines of the type described above, the volume of each auxiliary combustion chamber and the areas of the suction and discharge apertures must appropriately be selected so that stabilized combustion of the air-fuel mixture is achieved. Particularly, the sizes or areas of the above-mentioned suction and discharge apertures of the auxiliary combustion chamber must be such that the exhaustion of the residual gases from the auxiliary combustion chamber is promoted during the intake stroke of the engines. This is because the completeness of the exhaustion of the residual gas from the auxiliary combustion chamber has a large influence on the stability of the operation of internal combustion engines. In other words, it should be understood that when the exhaustion from the auxiliary combustion chamber is incomplete, failure of ignition of the rich air-fuel mixture within the auxiliary combustion chamber will often occur with the result that the operation of the internal combustion engine becomes unstable.